A triboelectric projector of pulverulent coating product is a projector in which the electrostatic charge of the coating product is obtained by rubbing contact of the particles of the coating product against one or more surfaces made of insulating material disposed along their path. A projector of this type generally comprises a channel for charging the coating product and is supplied from a source of coating product such as for example a reservoir of fluidized powder, through a supply conduit in which a mixture of air and of coating product circulates. It is known, for example by Application EP-A1-0 627 265, to provide an additional air admission in the projector near the admission of the conduit supplying the mixture of air and coating product.
In the known devices of the prior art, an essential problem resides in the fact that it is not possible to control the electrostatic charge obtained by friction by means of a simple parameter.
In fact, in the device of EP-A1-0 627 265, the air is injected substantially perpendicularly to the principal axis of the jet pipe of the projector, at right angles with respect to the admission of the conduit supplying the mixture of air and coating product. This generates turbulences in the mixture of air and coating product which create complex phenomena. These phenomena have an influence on the triboelectric charge obtained. In addition, such turbulences cause wear of the parts constituting the projector at the level of the admission chamber of the mixture of air and coating product, with the result that operations of maintenance of the projector must be provided at regular intervals.
The invention solves all these problems by proposing a triboelectric projector in which the triboelectric charge obtained may be controlled precisely thanks to the flowrate of air for dilution and/or acceleration injected in the projector and in which the phenomena of wear are reduced compared with the prior art.